An Improved Viscosity-Temperature Correlation for Crude Oils

The available data of crude oil viscosity over a temperature range 130-220°F and at atmospheric pressure are used to develop a method to predict the viscosity of crude oils. The proposed correlation based upon API gravity, and viscosity at reservoir temperature. The proposed new correlation has been verified using data base on crude oil of different densities, and it shows significantly better correlation, with an average absolute deviation (AAD) of 2.8%.     

Effects of Temperature and Pressure on Natural Gas Viscosity Which Has Different API Gravities

The theory of gas transport is simply stated, but it is quite complex to express in equations that can be used directly to calculate viscosity. A correlation was developed to predict viscosity of natural gas (of different API gravities) function of temperature and pressure. This correlation depends only on API gravity of natural gas. The proposed correlation has been verified using data of about 246 data points, and it is shows significantly better correlation, with an average absolute error of 3.2%.     

PAPR reduction for OFDM‐based visible light communication systems using proposed hybrid technique

Orthogonal Frequency Division Multiplexing (OFDM) is utilized with visible light communication (VLC) systems to decrease the impacts of inter‐symbol interference and to achieve communication with high speed of data transmission and huge bandwidth. In any case, the main problem in OFDM‐based VLC systems is high peak‐to‐average power ratios (PAPRs). This paper proposes a hybrid PAPR reduction technique based on signal transformation combined with clipping. The Hadamard transform is used in the proposed technique to reduce the PAPR without affecting the bit error rate (BER) of the VLC systems. The optimum clipping threshold at which the PAPR is reduced simultaneously with the improvement the BER of the VLC systems is also determined. The performance of the proposed system is assessed in terms of complementary cumulative distribution function and the BER. The obtained results demonstrate that the proposed procedure can simultaneously decrease the PAPR and achieve good BER performance compared to the OFDM‐based VLC system.     

1D p–n Junction Electronic and Optoelectronic Devices from Transition Metal Dichalcogenide Lateral Heterostructures Grown by One-Pot Chemical Vapor Deposition Synthesis

Lateral heterostructures of dissimilar monolayer transition metal dichalcogenides provide great opportunities to build 1D in-plane p–n junctions for sub-nanometer thin low-power electronic, optoelectronic, optical, and sensing devices. Electronic and optoelectronic applications of such p–n junction devices fabricated using a scalable one-pot chemical vapor deposition process yielding MoSe₂-WSe₂ lateral heterostructures are reported here. The growth of the monolayer lateral heterostructures is achieved by in situ controlling the partial pressures of the oxide precursors by a two-step heating protocol. The grown lateral heterostructures are characterized structurally and optically using optical microscopy, Raman spectroscopy/microscopy, and photoluminescence spectroscopy/microscopy. High-resolution transmission electron microscopy further confirms the high-quality 1D boundary between MoSe₂ and WSe₂ in the lateral heterostructure. p–n junction devices are fabricated from these lateral heterostructures and their applicability as rectifiers, solar cells, self-powered photovoltaic photodetectors, ambipolar transistors, and electroluminescent light emitters are demonstrated.     

Extended Elementary Siphons and Their Application to Liveness‐Enforcement of Generalized Petri Nets

As a significant structural object, siphons are extensively employed to implement a large number of deadlock prevention and liveness‐enforcing methods for flexible manufacturing systems modeled by Petri nets. By linear combinations, a set of elementary siphons is chosen from all strict minimal ones to be controlled and thus the structural complexity of a supervisor is greatly reduced. The concept of elementary siphons is originally proposed for ordinary Petri nets. When applied to generalized Petri nets, their selection and controllability require an additional study. In this work, the concept of augmented siphons is proposed to extend the application of the elementary ones to a class of generalized Petri nets, GLS³PR. Based on graph theory, a siphon extraction algorithm is developed to obtain all strict minimal siphons, from which augmented elementary ones are computed. In addition, the controllability conditions of dependent siphons are developed. Through fully investigating the net structure, especially weight information, the set of augmented elementary siphons is more compact and well suits for generalized Petri net models under consideration. Some examples are used to illustrate the proposed method.     

Bench Scale Studies for Pretreatment of Sanitary Landfill Leachate with Moringa Oleifera Seeds Extract

A laboratory study using a bench scale model of two unit operations involved processes of coagulation (using Moringa oleifera seeds as a natural coagulant) and flocculation-sedimentation have been adopted to treat the leachate from Air Hitam Sanitary Landfill at Puchong in Malaysia. The results of this study has shown, that M. oleifera has a potential for the removal of heavy metals from the leachate, and may be used as a pre-treatment stage for biological treatment to eliminate a portion of the toxic heavy metals, which limit the activity of micro-organisms in the leachate.     

A Chaotic Interleaving Scheme for the Continuous Phase Modulation Based Single-Carrier Frequency-Domain Equalization System

In this paper, we propose a chaotic interleaving scheme for the continuous phase modulation based single-carrier frequency-domain equalization (CPM-SC-FDE) system. Chaotic interleaving is used in this scheme to generate permuted versions from the sample sequences to be transmitted, with low correlation among their samples, and hence a better bit error rate (BER) performance can be obtained. The proposed CPM-SC-FDE system with chaotic interleaving combines the advantages of the frequency diversity, the low complexity, and the high power efficiency of the CPM-SC-FDE system and the performance improvements due to chaotic interleaving. The BER performance of the CPM-SC-FDE system with and without chaotic interleaving is evaluated by computer simulations. Also, a comparison between the proposed chaotic interleaving and the conventional block interleaving is performed. Simulation results show that, the proposed chaotic interleaving scheme can greatly improve the performance of the CPM-SC-FDE system. Furthermore, the results show that this scheme outperforms the conventional block interleaving scheme in the CPM-SC-FDE system. The results also show that, the proposed CPM-SC-FDE system with chaotic interleaving provides a good trade-off between system performance and bandwidth efficiency.     

Broadening the polyethylene molecular weight distribution by controlling the hydrogen concentration and catalyst feed rates

This paper discusses the control of an industrial gas-phase polyethylene reactor to produce a desired molecular weight distribution (MWD) of the polymer. The controller objective is to regulate online the entire molecular weight distribution by either manipulating the hydrogen content inside the reactor or coordinating the feed rates of two different types of catalysts. In this work, the molecular weight distribution is modeled as a function of the reaction kinetics and hydrogen to monomer ratio. Nonlinear model predictive controller (NLMPC) algorithm is used to maintain the desired molecular weight distribution online. The closed-loop simulations indicated the effectiveness of NLMPC to achieve its goal even in the presence of modeling errors. Moreover, the results showed that, altering the hydrogen concentration solely can produce the required polymer quality provided that an efficient mechanism is available to readily alter the hydrogen composition. Alternatively, the desired MWD can also be guaranteed with proper manipulation of the catalyst feed rates while the other process inputs are kept constant.     

Synthesis, Surface, Thermodynamic Properties of Some Biodegradable Vanillin-Modified Polyoxyethylene Surfactants

Four water-soluble non-ionic ethoxylated surfactants based on vanillin were synthesized (VE₁₅, VE₂₀, VE₄₀, and VE₆₀). The chemical structures of these surfactants were confirmed using FT-IR and ¹H-NMR spectra. The molecular weights of the compounds were determined using viscosity measurements and gel permeation chromatography. Surface tension as a function of the concentration of the surfactant in aqueous solution was measured at 25, 40 and 55?°C. From these measurements, the critical micelle concentration (CMC), effectiveness (??_cmc), efficiency (pC₂₀), maximum surface (??_max) excess and minimum surface area (A _min), were calculated. The surface activity measurements showed their high tendency towards adsorption and micellization and their good surface tension reduction, and low interfacial tension. The emulsion stability measurements showed the applicability of these surfactants as emulsifying agents. The thermodynamic parameters of micellization (??G _mic, ??H _mic, ??S _mic) and adsorption (??G _ads, ??G _ads, ?S _ads) showed their tendency towards adsorption at the interfaces and also micellization in the bulk of their solutions. The biodegradability of the prepared surfactants was tested in river water using die-away method and showed their readily biodegradation in the open environment.     

Antimicrobial activity of functionalised carbon nanotubes against pathogenic microorganisms

Carbon nanotubes represent one of the best examples of novel nanostructures, exhibit a range of extraordinary physical properties, strong antimicrobial activity and can pierce bacterial cell walls. This investigation handles the antimicrobial activity of functionalised multiwall carbon nanotubes (F‐MWNTs) as an alternative antimicrobial material compared to the commercial antibiotics. Antibacterial activities of F‐MWNTs are investigated through two different kinds of bacteria, E. coli and S. aureus. The results demonstrate that the best concentration of F‐MWNTs for the maximum inhibition and antibacterial functionality is 80 and 60 μg/ml for E. coli and S. aureus, respectively. The transmission electron microscope reveals the morphological changes damage mechanism for the cellular reliability on these microorganisms. F‐MWNTs are capable of biologically isolating the cell from their microenvironment, contributing to the development of toxic substances and placing the cell under oxidative stress leading to cellular death. The efficiency of F‐MWNTs is compared with the common antibiotics and shows an enhancement in the inhibitory effect with percentages reaches 85%. To account for the bactericidal performance of F‐MWNTs towards these pathogens, the dielectric conductivity and the bacterial growth measurements are conducted. The present study endeavour that F‐MWNTs could be exploited in biomedical devices and altering systems for hospital and industrial cleaning applications.Inspec keywords: antibacterial activity, biomedical materials, microorganisms, cellular biophysics, toxicology, nanomedicine, multi‐wall carbon nanotubes, transmission electron microscopy, electrical conductivity, permittivityOther keywords: F‐MWNTs, pathogenic microorganisms, antimicrobial activity, bacterial cell walls, functionalised multiwall carbon nanotubes, antibacterial activity, E. coli, S. aureus, antimicrobial material, physical properties, transmission electron microscopy, morphological changes, damage mechanism, cellular reliability, microenvironment, toxic substances, oxidative stress, cellular death, bactericidal performance, dielectric conductivity, bacterial growth measurements, biomedical devices, C